The present invention relates generally to synthetic aperture radar imaging systems and more specifically to an autofocus image processing system for estimating image displacement relative to a reference frame.
A large class of problems involving image processing are a result of the need for an accurate registration cability. This task has been alleviated to some degree by the prior art techniques given in the following patents:
U.S. Pat. No. 4,330,833 issued to Pratt et al on 18 May 1982;
U.S. Pat. No. 4,244,029 issued to Hogan et al on 6 Jan 1981;
U.S. Pat. No. 3,955,046 issued to Ingham et al on 4 May 1976;
U.S. Pat. No. 3,943,277 issued to Everly et al on 9 Mar 1976;
U.S. Pat. No. 4,162,775 issued to Voles on 31 Jul 1979;
U.S. Pat. No. 4,368,456 issued to Forse et al on 11 Jan. 1983;
Pratt et al disclose a method and apparatus for digital image processing which operates on dots or "pixels" with an operator matrix having dimensions smaller than a conventional operator. It may be used in the restoration improvement of photographs or other images taken by satellites or astronauts in outer space and then transmitted to earth. Hogan et al disclose a digital video correlator in which a reference image and a live image are digitized and compared against each other in a shifting network to determine the correlation between the two images. In Ingham et al phase shifts are detected and used to follow a target. Correlation type trackers are also disclosed in the Everly and Voles patents. Forse et al teach an image correlator in which a reference representation is updated by a control processor when the correlation of it with a current representation reaches a peak.
In view of the foregoing discussion it is apparent that in the realm of synthetic aperture radar imaging systems there exists a need for development in the area of accurate imaging, particularly if the amount of available data is space. The present invention is directed towards satisfying that need.